1. Field of the Invention
The present invention relates to a method for manufacturing an aminoalcohol. More particularly the present invention relates to a method for manufacturing an aminoalcohol, classified as a tertiary amine, in which one or more of the three substituents bonded to the nitrogen atom of the amino group are carbon-skeleton organic group(s) (such as alkylene group(s)) which have four or five carbon atoms in their carbon-skeleton(s) and link hydroxyl group(s) to the nitrogen atom of the amino group. The present invention also relates to a method for manufacturing an aminoalcohol, classified as a primary or secondary amine, in which the substituent(s) bonded to the nitrogen atom of the amino group are carbon-skeleton organic group(s) (such as alkylene group(s)) which have four or five carbon atoms in their carbon-skeleton(s) and link hydroxyl group(s) to the nitrogen atom of the amino group.
2. Description of the Related Art
Ethanolamines such as 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, and 2-(dibutylamino)ethanol are currently being manufactured industrially as aminoalcohols classified as tertiary amines. N-alkyldiethanolamines, triethanolamine, and other such ethanolamines are also aminoalcohols that can be used industrially at the present time. These ethanolamines are synthesized by reacting an alkylamine or ammonia and ethylene oxide (see, for example, U.S. Pat. No. 5,663,444).
Of the aminoalcohols classified as tertiary amines, those other than ethanolamines are not manufactured industrially, but there are reports of methods for synthesizing 4-(dimethylamino)-1-butanol, for example, such as the following (i) and (ii).
(i) It is stated in the Journal of Organic Chemistry (22, 1225 (1957)) that 4-(dimethylamino)-1-butanol is obtained by putting .gamma.-butyrolactone and dimethylamine in a sealed tube and reacting them for 4 hours at 150.degree. C. to form N,N-dimethyl-.gamma.-hydroxybutylamide, and then reacting this with lithium aluminum hydride in an ether solvent.
(ii) It is stated in the specification of West German Patent No. 857501 that 4-(dimethylamino)-1-butanol is obtained by allowing lithium aluminum hydride to act on N,N-dimethylsuccinamic acid.
Of the aminoalcohols classified as primary amines, examples of compounds being manufactured industrially at present include 2-aminoethanol and 3-amino-1-propanol. The former (2-aminoethanol) is manufactured by reacting ethylene oxide and ammonia (eg, Japanese Patent Application Laid-Open No. H11-90238), while the latter (3-amino-1-propanol) is manufactured by reducing 3-hydroxypropiononitrile in the presence of a Raney nickel catalyst or the like (eg, Japanese Patent Application Laid-Open No. S64-9963).
Of the aminoalcohols classified as secondary amines, examples of compounds being manufactured industrially include ethanolamines such as 2-(methylamino)ethanol. Ethanolamines such as these are manufactured by reacting an alkylamine with ethylene oxide.
However, with the above-mentioned methods for synthesizing ethanolamines classified as tertiary amines, because the number of carbon atoms in the ring of the raw material ethylene oxide is 2, it follows that the number of carbon atoms in the main chain of the alkylene groups between the amino groups and hydroxyl groups in the resulting aminoalcohol is limited to 2.
Synthesis methods such as the above-mentioned (i) and (ii) have been reported for aminoalcohols in which there are three or more carbon atoms in the main chain of the alkylene groups between the hydroxyl groups and the nitrogen atoms of the amino groups, but when viewed from an industrial standpoint, all of these methods have drawbacks in terms of the reaction raw materials, reaction time, treatment after the reaction, reaction equipment, and so forth. For instance, the above-mentioned methods (i) and (ii) both entail the use of lithium aluminum hydride, which has low handleability and is expensive, so they are hardly industrially advantageous methods.
Also, because of limitations imposed by the raw materials used or the reaction route, the number of carbon atoms in the main chain of the alkylene groups between the nitrogen atoms of the amino groups and the hydroxyl groups of the above-mentioned aminoalcohols classified as primary or secondary amines is necessarily limited to 2 or 3 for the former and 2 for the latter.
Therefore, the problem with the above ways of manufacturing an aminoalcohol with four or more (and particularly 4 or 5) carbon atoms between the hydroxyl group and the nitrogen atom of the amino group was that industrial manufacture was unfeasible.
By the way, 4-amino-2-methyl-1-butanol or 5-(methylamino)-1-pentanol has been reported as an aminoalcohol that is classified as a primary amine or secondary amine, that has 4 or 5 carbon atoms in the main chain of the alkylene group between the hydroxyl group and the nitrogen atom of the amino group, and that has been synthesized in the laboratory. Specifically, the former has been synthesized in the laboratory by reacting 2-methyl-4-aminobutyric acid with lithium aluminum hydride in a tetrahydrofuran solvent for 6 hours under reflux conditions (J. Amer. Chem. Soc., 81, 4946 (1959)). The latter has been synthesized in the laboratory by mixing hydrochloric acid and dihydropyran, then adding an aqueous methylamine solution to this mixture, extracting and condensing the crude reaction solution thus obtained, then reacting this product with sodium borohydride in an ethanol solvent, in the isolated yield of 21% based on the dihydropyran (J. Chem. Soc. Perkin Trans. I, 1375 (1989)). Therefore, it may be supposed that these experimental manufacturing processes could be applied to industrial manufacture.
These experimental manufacturing processes can hardly be considered industrially advantageous methods, however, because they require the use of lithium aluminum hydride, dihydropyran, sodium borohydride, and other such expensive reaction raw materials, the reaction raw materials have low handleabilities, the treatment after the reaction is troublesome, and new reaction equipment has to be installed.